This invention relates to vibration control and isolation systems and is related generally to applicant's prior U.S. Pat. No. 3,701,499 which discloses a variety of vibration control and isolation systems employing acceleration sensors and feedback loops containing signal components derived from acceleration and other quantities.
The systems described in applicant's prior patent suggest various electronic compensation circuits for feedback signals and also the possibility of employing velocity sensors. No system is shown or suggested which employs velocity sensor derived signals which are modified electronically to provide a vibration isolation system that reduces transmitted or induced vibrations by a large factor for all frequencies above an extremely low frequency, approaching zero, with stability assured for all frequencies.
The combination of passive and active vibration control systems has been analyzed in a paper by a Guntur and Sankar entitled "Fail-Safe Vibration Control Using Active Force Generators" published by the American Society of Mechanical Engineers in the transactions, Journal of Mechanical Design, Paper No. 81-DET-85. The generalized form of a combined active and passive system is illustrated in FIG. 3 of this article and the transmissability characteristic of a velocity analog force feedback system is shown in FIG. 4 for various values of gain. The description is with reference to the theoretical "sky-hook" damper without reference to the sensor for derivation of the velocity signal or the requirements for maintaining stability throughout the frequency range of operation.